1. Field of the invention
This invention relates to a refrigerator including a cold storage evaporator for cooling a cold storage compartment and a freezer evaporator for cooling a freezer compartment and carrying out a cold storage cooling mode in which the cold storage compartment is cooled by the cold storage evaporator and a freezer cooling mode in which the freezer compartment is cooled by the freezer evaporator, alternately.
2. Description of the prior art
In conventional household refrigerators, refrigerant discharged from a compressor is caused to flow through a condenser, a throttle valve (a capillary tube), an evaporator and the compressor, whereby a refrigerating cycle is constituted. A single evaporator is utilized to cool both a cold storage compartment and a freezer compartment both having different temperature ranges. A temperature sensor is provided for detecting a temperature in the freezer compartment, thereby generating a temperature signal. The compressor and an air circulation fan are controlled to be turned on and off on the basis of the temperature signal so that the temperature in the freezer compartment is controlled. Further, a damper is opened and closed so that a temperature in the cold storage compartment is controlled. In the aforesaid construction, however, it is difficult to accurately control the temperatures in the cold storage and freezer compartments respectively, and a cooling efficiency is low.
In view of the aforesaid problems, the prior art has recently proposed a refrigerator including a cold storage evaporator for cooling a cold storage compartment, a freezer evaporator for cooling a freezer compartment and a flow-path switching valve for switching refrigerant from the compressor between a case where the refrigerant is caused to flow through the cold storage evaporator and a case where the refrigerant is caused to flow through the freezer evaporator, alternately, so that the cold storage and freezer compartments are alternately cooled. Further, in the proposed refrigerator, an operating frequency of the compressor is varied so that the temperatures in the compartments are rendered suitable for the respective compartments. Japanese Patent Application Nos. 9-340377 and 10-192028 disclose refrigerators constructed as described above respectively.
In the proposed refrigerator, the cooling performance is variable according to an amount of load accommodated in the refrigerator. Repeated on-off of the compressor results in cycle loss. Accordingly, the compressor is continuously operated and is not stopped at a normal room temperature for the purpose of reducing the cycle loss and limiting increases in input power and noise at the time of starting of the compressor. However, the compartments are excessively cooled even in the case where the compressor is operated at its lower limit operating frequency when the room temperature is at or below 10xc2x0 C., for example. As a result, the compressor cannot sometimes be operated continuously. In this case, the compressor is stopped. At this time, when the compressor is stopped under the freezer compartment cooling mode in which the flow-path switching valve causes the compressor to communicate with the freezer compartment evaporator, high temperature refrigerant at the high pressure side flows into the freezer compartment evaporator. Consequently, the temperature of the freezer compartment evaporator becomes higher than those of the compartments. This reduces the cooling efficiency of the compressor when re-started.
Therefore, an object of the present invention is to provide a refrigerator including a first or cold storage evaporator for cooling a first or cold storage compartment and a second or freezer evaporator for cooling a second or freezer compartment and carrying out a first or cold storage cooling mode in which the cold storage compartment is cooled by the cold storage evaporator and a first or freezer cooling mode in which the freezer compartment is cooled by the freezer evaporator, alternately, wherein the high temperature refrigerant can be prevented from entering the freezer compartment evaporator when the compressor is stopped, so as to limit an increase in the temperature of the freezer compartment evaporator.
The present invention provides a refrigerator comprising a first compartment, a second compartment, a compressor compressing and discharging refrigerant, a first evaporator connected to the compressor to cool the first compartment, the first evaporator having an outlet, a second evaporator connected to the compressor in parallel with the first evaporator to cool the second compartment, the second evaporator having an outlet, a check valve connected between the outlets of the first and second evaporators to prevent the refrigerant out of the first evaporator from entering the second evaporator, a flow-path switching element for switching a cooling mode between a first cooling mode in which the refrigerant discharged from the compressor is caused to flow through the first evaporator to thereby cool the first compartment and a second cooling mode in which the refrigerant discharged from the compressor is caused to flow through the second evaporator to thereby cool the second compartment, and a control device provided for controlling the compressor and the switching element so that the first and second cooling modes are switched alternately and so that the compressor is stopped under the first cooling mode with drop of the temperature in the either compartment.
In the first cooling mode, the compressor communicates with the first or cold storage evaporator though shut off from the second or freezer evaporator. When the compressor is stopped in this state, no high temperature refrigerant enters the second evaporator from the high pressure side. Moreover, since the check valve at the outlet side of the second evaporator is actuated, no refrigerant flows backward from the first evaporator to the second evaporator. Consequently, high temperature refrigerant can be prevented from entering the second evaporator upon stop of the compressor, whereupon increase in the temperature of the second evaporator can be limited.
In a first preferred form, the refrigerator further comprises a defrosting heater for defrosting the second evaporator, and the control device controls the compressor so that the operation of the compressor is stopped under the second cooling mode when the second evaporator is defrosted by the defrosting heater. In the second cooling mode, the compressor communicates with the second evaporator. When the compressor is stopped in this state, high temperature refrigerant flows into the second evaporator from the high pressure side. Thus, positive inflow of the high temperature refrigerant enhances increase in the temperature of the second evaporator, thereby reducing a defrosting time for the second evaporator.
In a second preferred form, the control device controls the compressor so that the compressor is re-started under the second cooling mode after the second evaporator has been defrosted. Low temperature refrigerant can be retained in the second evaporator under the second cooling mode. Since cooling is performed by a suitable amount of refrigerant in a subsequent first cooling mode, back flow of excess refrigerant can be prevented, and efficient cooling can be performed with a suitable amount of refrigerant in each cooling mode.
In a third preferred form, the refrigerator further comprises two defrosting heaters for defrosting the first and second evaporators respectively, and the control device controls the defrosting heaters so that either evaporator not in operation is defrosted by the corresponding defrosting heater during execution of either cooling mode. Since each evaporator is defrosted when necessary and the compressor need not be stopped, a useless temperature increase with stop of the compressor can be prevented at the side of the evaporator which need not be defrosted.
In a fourth preferred form, the control device controls the compressor and the flow-path switching element so that the second cooling mode is first carried out when the refrigerator is connected to a power supply. In the fourth preferred form, too, low temperature refrigerant can be retained in the second evaporator under the second cooling mode. Since cooling is performed with a suitable amount of refrigerant in a subsequent first cooling mode, back flow of excess refrigerant can be prevented, and efficient cooling can be performed with a suitable amount of refrigerant in each cooling mode.